Aug 10, 2012 5:44 PM by Meteorologist Mike Rawlins
Thanks to an area of low pressure, Montana will get in on some cooler air this weekend.
The low will be responsible for numerous showers and thunderstorms through Friday night, but drier air will move in again for Saturday.
Most areas will only reach the mid to upper 80s over the weekend under mostly sunny skies.
High pressure will build in again for Monday, warming us back into the low 90s-- only for a day.
Current model runs still show cooler air arriving during the middle part of the week.
I've seen some considerable timing differences run-to-run over the last few days, so I don't have a ton of confidence on when the cold front will make it through Montana.
Right now, our best forecast is for Tuesday-Wednesday.
This will allow much cooler air into our area, dropping temperatures well below-average.
When piecing together our forecast for use on-air or online, we use a variety of different computer models.
These models often come up with different solutions for the expected weather.
Our knowledge of how the models work and their biases helps the STORMTracker Weather Team come up with the best possible forecast.
I say this because there are quite a few differences in two very important models for next week.
The Global Forecast System model (GFS) shows rain/storms affecting central and southern Montana midday Wednesday.
This snapshot is from the 12Z Friday (6 am MDT) run of the model and shows the forecast for noon Wednesday.
Notice the bullseye of green/yellow right over central Montana, indicating some decent rainfall.
This doesn't line up with another model we use every day.
The European Centre for Medium-Range Weather Forecasts model (ECMWF) is also very reliable at predicting atmospheric conditions days in advance.
This morning's 12Z (6 am MDT) run shows showers and storms affecting north central Montana Tuesday night, spreading farther south with time.
We will have to watch how the models resolve this timing difference over the coming days.
Fow now, expect a chance of rain on Wednesday with temperatures in the 70s.